Oxide semiconductor technology has various advantages, as compared with the existing silicon (Si)-based device.
A first advantage in optical terms is that an oxide semiconductor may form a transparent thin film. The existing semiconductor such as a Si or GaAs semiconductor to be compared with the oxide semiconductor has a band gap of 1.2 eV and 1.43 eV, respectively, and when it is irradiated with visible light having energy above the band gap, it loses light energy by the phenomenon that electrons in a valence band are excited to a conduction band, which causes decrease of transmitted light energy. In comparison, since the oxide semiconductor such as ZnO, or Ga2O3, In2O3 or SnO2 has a broad band gap of about 3.1 eV or more, it does not absorb, but transmits visible light, and thus, is usable as a transparent display device.
Secondly, in electrical and electronic terms, the oxide semiconductor has high carrier mobility (1-100 cm2/Vs), and thus, also has an excellent electrical performance.
As a third advantage, the oxide semiconductor has polycrystalline and monocrystalline structures even at a room temperature, so that it is possible to manufacture a thin film transistor having good properties without a separate heat treatment (annealing) process.
Meanwhile, one-dimensional nanomaterials such as a nanorod, a nanowire, and the like refer to materials having a diameter of several nanometers to tens of nanometers, and a length of hundreds of nanometers to several micrometers. Such one-dimensional nanomaterials show various physical and chemical properties which have not been seen in the existing bulk materials, and using such properties, many applications as basic materials for the development of a nanodevice are expected.
The one-dimensional nanostructures using the metal oxide show excellent light transmittance, a high piezoelectric index, and a UV emitting property, and thus, it has been applied to various kinds of devices such as a transparent electrode of a UV-emitting diode or a laser diode, a photovoltaic device, an optical waveguide, and a gas sensor as base materials for implementing an electronic device, an optical device or a sensor in a nano size. Therefore, as the metal oxide nanostructure has an important role in manufacturing nanoscale devices, much attention is drawn to the synthesis method and the development of high-quality one-dimensional metal oxide nanostructures.
Representatives of the method of synthesizing the metal oxide nanostructure include a VLS (vapor-liquid-solid) method, a CBD (chemical-bath-deposition) method, and the like. The manufacturing process by the VLS method may relatively easily control the orientation of a zinc oxide nanostructure, but requires a growing condition such as a high vacuum condition and a high temperature, and has disadvantages such as difficulty in mass production, an expensive equipment price, much time required for the manufacture, and the like. Since the manufacturing process by the CBD method has various advantages of being simple, allowing synthesis at low temperature, and performing synthesis in a large area, many studies thereof have been made. Among them, a hydrothermal synthesis method which is the most representative method, is capable of growing the metal oxide nanostructure at relatively low temperature under a normal pressure, and thus, many studies thereof have been made.
Korean Patent No. 10-1340953 suggests a method of preparing a zinc oxide nanorod pattern in which hydrothermal synthesis occurs by supplying thermal energy for hydrothermal synthesis from laser irradiation, and at the same time, patterning is performed using a laser direct lithography apparatus, so that the process has excellent energy economics, and is feasible at a low cost within a short time; and patterns are prepared with a group of zinc oxide nanorods having desired size and density by controlling laser irradiation time, so that the method is easily usable in manufacturing a micro electronic apparatus, an optoelectronic device, an optical memory apparatus, a chemical sensor, a biosensor, and the like; and a zinc oxide nanorod pattern prepared thereby.
However, there are some problems that the laser of Korean Patent No. 10-1340953 uses a continuous laser, the nanostructure prepared by the method has low density, the shape of the nanostructure may not be precisely adjusted, and if the nanostructure is prepared using the continuous laser, it is not formed in a radial form as shown in FIG. 1, and thus, may not be used as a solder structure.